You're right about your translation. It not only does not convey the intended "even", but the first part translates back to:
"Those who complain to their work, working partners, and even their company while still taking their salary...."
Suggested Translation for the first part:
This phrase emphasizes that even though state B is continuing state A is also still continuing. In this case I think this would be one of the better ways to express "...while still taking/receiving their salary..."
I think it is perfectly fine to stick with "文句を言う" but "愚痴をこぼす" is another good one if you would like. As far as expressing that they are "continuing to complain", I like using the 連体形 + "まくる" form, but that is entirely up to preference and is sort of casual too. If you want to sound more neutral you could just replace "まくる" with "つづける", or you can just say "絶えず言ってしまう".
I know I didn't touch on the latter half of your sentence at all. That is because I don't think you should try to translate it literally. At best, literal translations of most metaphors only ambiguously keep their meaning in Japanese. I suggest looking up actual Japanese metaphors that carry the same volitional meaning. For example:
This is by no means the best metaphor out there (it's actually the only one I can think of right now...), but if you search you may find something that you like more.
Edits for English grammar errors and a forgotten も.